Special Issue Information

Dear Colleagues,

Nitrogen (N) and phosphorus (P) nutrition of trees has been studied for many decades, but has largely been focused on inorganic nutrient uptake and leaf level nutrient contents. In recent years it became obvious that N and P cycling at the ecosystem level is of vital importance for tree nutrition and that organic N uptake by trees is an essential part of ecosystem N cycling; in particular on N and/or P poor soils, and in cooler climates. The significance of organic P uptake by trees is still a matter of debate, especially under field conditions. The overlay of climate change on ecosystem N and P cycling has become an important issue of forest research. This overlay raises questions around competition for N and P among structural elements (overstorey vs. undestorey), as well as among dominant species. Many nutritionally related aspects of changing climates, such as effects on rhizosphere and phyllosphere, remain seriously under-studied. The central aim of this Special Issue is to provide new insights into some of these topics at the tree, and the ecosystem level.

Prof. Dr. Heinz RennenbergProf. Dr. Mark A. AdamsGuest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Forests is an international peer-reviewed Open Access monthly journal published by MDPI.

Abstract: Distinct seasons and diverse tree species characterize temperate deciduous forests in NE Asia, but large areas of deciduous forests have been converted to conifer plantations. This study was conducted to understand the effects of seasons and tree species on leaf litter decomposition in a temperate forest. Using the litterbag method, the decomposition rate and nitrogen, phosphorous, and carbon dynamics of Mongolian oak (Quercus mongolica), Korean pine (Pinus koraiensis), and their mixed leaf litter were compared for 24 months in a Mongolian oak stand, an adjacent Korean pine plantation, and a Mongolian oak—Korean pine mixed stand. The decomposition rates of all the leaf litter types followed a pattern of distinct seasonal changes: most leaf litter decomposition occurred during the summer. Tree species was less influential on the leaf litter decomposition. The decomposition rates among different leaf litter types within the same stand were not significantly different, indicating no mixed litter effect. The immobilization of leaf litter N and P lasted for 14 months. Mongolian oak leaf litter and Korean pine leaf litter showed different N and P contents and dynamics during the decomposition, and soil P2O5 was highest in the Korean pine plantation, suggesting effects of plantation on soil nutrient budget.

Planned Papers

The below list represents only planned manuscripts. Some of these
manuscripts have not been received by the Editorial Office yet. Papers
submitted to MDPI journals are subject to peer-review.

Type of manuscript: ArticleTitle: Quantification of bioavailable phosphorus in the ectomycorrhizal rhizosphere of mature loblolly pinesAuthors: Bradley W MillerAffiliations: US Environmental Protection Agency, USAAbstract: Tree growth in southern pine plantations is typically limited by nitrogen (N) and phosphorus (P) availability in the soil environment. Over time, P in soils is sorbed to or diffuses within poorly crystalline Fe and Al oxides minerals. A variety of plants, microbes, and mycorrhiza exude ligands such as low-molecular-mass organic acids (LMMOA) to increase P uptake in soils with low bioavailable P. Agerer (2001) suggested that ectomycorrhiza may be group based upon the exploration strategies of their emanating hyphae and thus making inferences about ecophysiological effects. In this study we extracted P from the ectomycorrhizal rhizosphere to test for long-term fertilizer effects on bioavailable P pools among ectomycorrhizal exploration strategies. Bioavailable P was quantified by comparing P desorption in the bulk soil and ectomycorrhizal rhizosphere with increasing concentrations of oxalic acid. The concentration of P desorbed from mineral surfaces in the bulk soil increased significantly when oxalate exceeded 20 μmol g-1 soil. However, there was a significant decrease in oxalate dissolvable P pools in the ectomycorrhizal rhizosphere at 20 μmol oxalate g-1 soil compared to bulk soil. Fertilization increased biologically available P pools by 396%. There were no significant differences in the bioavailable P pools among exploration strategies encountered. These results suggest the long-term affects of fertilization is an increase in bioavailable P pools in the ectomycorrhizal rhizosphere without increasing oxalate exchangeable P in the bulk soils.

Type of manuscript: ArticleTitle: Influence of litterfall patterns on soil nutrient quality in an Indian tropical deciduous forest ecosystem.Author: Pankaj Kumar SrivastavaAbstract: Forest affects the nutrient composition of soil through nutrient inputs via litterfall. Nutrient properties and enzyme activities of soils were examined under the influence of litterfall of the natural Dry Miscellaneous forest (DM), natural Sal (Shorea robusta) Mixed forest (SM) and a 50 years old commercial Teak (Tectona grandis) Plantation forest (TP) in a tropical deciduous forest of Northern India. Annual litterfall was 6.7, 5.9 and 5.0 Mg ha-1 in the DM, SM and TP, respectively. The highest annual nutrient concentrations (4.46% N, 0.588% P and 0.773% K) noted in the DM litter and lowest in the TP litter. Total organic carbon and microbial biomass carbon in soils were maximum as 1.99% and 836 µg g-1, respectively, and minimum as 0.57% and 101 µg g-1, respectively in the DM. The N (0.19%), P (664 mg g-1) and K (5473 mg g-1) were highest in the DM soil and lowest in the TP soil. Likewise, the soil enzyme activities were followed the same pattern. The natural DM and SM forests with higher basal area and density contributed the higher nutrient inputs via litterfall comparatively to the TP. In natural forests, higher nutrients might lead to the higher soil nutrient properties and enzyme activities compared to the monoculture commercial plantations.Keywords: dry miscellaneous forest, Shorea robusta, teak plantation, litter, soil.

Type of manuscript: ArticleTitle: Evaluating nitrogen transfer from Caragana Shelterbelt and its effects on yield and nutrition of forage cropsAuthors: Gazali Issah1, Anthony Kimaro2, John Kort3, Diane Knight1Affiliations:1Soil Science Department, University of Saskatchewan, Saskatoon 2World Agroforestry Centre, Dar-es-Salaam, Tanzania 3Agroforestry Development Center, Agriculture and Agri-Food Canada, Indian Head, CanadaAbstract: The overuse of synthetic nitrogen (N) fertilizer to meet the requirements of food and forage crops species contributes to environmental problems such as nitrate leaching to groundwater and enhanced greenhouse effects through N­2O emissions. Agricultural practices integrating legumes and food or forage crops can address this problem by reducing the reliance on industrial fertilizers through fixation and transfer of N by legumes to associated crops. Below-ground N transfers in various systems have been widely researched. However, within the prairies, there is dearth of information regarding N transfer in shelterbelt-based systems. The field experiment was conducted to determine the amount of N transferred from Caragana shelterbelt to forage crops (triticale and oats) using the 15N natural abundance technique and to assess effects of this transfer on forage biomass and quality. Plants close to the shelterbelt row received significantly higher % N and actual N transferred compared to those further away. The range of the % N transfer spanned from 8-64 % and 16-70 % for the 2011 and 2012 seasons, respectively. This amount was equivalent to the transfer of 0.73-3.20 g N m-2 and 1.12-2.28 g N m-2 in triticale and oats, respectively, and it was within the optimum N application rates for these crops. The below-ground N transfer reached the optimum N rates even up to 20 m away from the shelterbelt. Total N and crude protein of the test crops improved significantly with the distance from the shelterbelt, signifying that the amount of N transferred enhanced forage crops nutrition. Biomass yield was, however, not affected suggesting that N may not be the main factor driving crop growth in the study site. The finding from the study may be indication that the N requirements of the forage species can be met by N from the shelterbelt.Keywords: agroforestry, nutrient management, 15N natural abundance, forage quality

Type of manuscript: ArticleTitle: Nitrogen fixation by legume trees, lianas and shrubs: their role in the N cycle of tropical and south temperate forests.Author: Janet I SprentAffiliation: Emeritus Professor of Plant Biology University of Dundee, Hon Research Fellow, James Hutton Institute, Research Associate, Royal Botanic Garden Edinburgh, UKAbstract: Not all woody legumes can nodulate: of those that can, not all do so under all conditions. They may be limited by climatic and edaphic factors, presence of suitable rhizobia and other microflora. Their importance varies with both latitude and longitude Dogmas drawn up for agricultural crops seldom apply to forest systems. This review will cover recent work on the following topics: Geographical considerations: latitude, longitude, wet and dry tropics and temperate regions Nitrogen transfer between forest species, including from nodulated legumes to woody parasites such as sandalwood and Nuytsia Facultative v. obligate fixation; the so-called nitrogen paradox in Central American forests. Nitrogen fixation in soils very low in certain nutrients such as P and excess of others, such as Al (and sometimes P). The role of soil microflora, especially rhizobia (both alpha and beta) and nodule occupancy by other, non-fixing bacteria; interactions with P acquisition systems such as mycorrhizas and cluster roots.